This invention relates to apparatus for processing semiconductor wafers in a vacuum and, in particular, to a compact apparatus having fewer joints and chambers than previous designs.
In the semiconductor industry, as in others, contamination by unwanted particles remains a continuing problem. Source of particles are legion and equipment makers continuously seek ways to reduce contamination. One approach, the "clean room", has been refined over the years to the point where a room in which wafers are processed is made very clean, and very expensive, even without any equipment in it.
In processes where a wafer is treated under vacuum, e.g. plasma etch or deposition, annealing, sputtering, etc., one has the potential of obtaining a very clean, and small, environment for the wafers. One approach in this area, for example as shown by U.S. Pat. No. 4,487,678, is to provide load locks for the wafers, i.e. one or more intermediate chambers isolate the processing chamber from ambient atmosphere. While this does provide good control over the local atmosphere, adjacent the wafers, the number of seals which must be made and broken to obtain this control reduces the overall reliability of the equipment as well as increase its cost. Further, in the event of a failure or routine maintenance, the process chamber is usually opened to atmosphere. Thus, one must carefully purge all the chambers to obtain the benefits of the several load locks. The purging can take a considerable length of time, depending roughly on the volume to be purged.
Load locks of the prior art are typically separated from each other, or ambient pressure, by gate valves. These valves require additional mechanization. As such, there are additional moving parts right at a location through which the wafer passes on its way to or from processing. The additional complexity produces particles which can contaminate the wafer. Thus, even if gases deleterious to a process are removed, contamination of the wafer can still occur.
In view of the foregoing, it is therefore an object of the present invention to provide a plasma reactor having two chambers isolated from each other without the use of a gate valve.
Another object of the present invention is to provide an improved plasma reactor apparatus having minimal volume for purging.
A further object of the present invention is to provide an improved plasma reactor apparatus in which contamination from particles is minimized.